Patent Application
20100286377
This invention relates to attachment chemistries for binding biomolecules to a substrate surface. More particularly, this invention relates to attachment chemistries involving branched structures for providing biomolecules having multiplicities of chemical binding moieties for binding the biomolecules to a substrate surface.
The following description provides a summary of information relevant to the present invention. It is not an admission that any of the information provided herein is prior art to the presently claimed invention, nor that any of the publications specifically or implicitly referenced are prior art to the invention.
The immobilization of oligonucleotides on substrates is an important and necessary step for many applications such as DNA chip technology, surface plasmon resonance experiments, or other biosensor applications. Classically, oligonucleotides are immobilized onto substrates by modification of the 3′- or 5′-end with one reactive group e.g. an amine, thiol or aldehyde (covalent attachment) or group forming stable complexes e.g. biotin, phenylboronic acid etc. (noncovalent attachment). The modified oligonucleotides are then addressed to the location where the immobilization is desired and reacted with an appropriate functional group such as an aldehyde, maleimide, hydrazide etc. or complexed with a binding molecule such as streptavidin, etc. The addressing to specific locations on a substrate can be done by spotting (pin or drop deposition), by electronic addressing, or by a variety of other processes. In some cases the reaction for the immobilization is slow and requires long (overnight) incubation of the oligonucleotides on the substrate. These immobilization reactions may also be reversible, resulting in the release of the biomolecule over time.
In other instances, dendrimeric structures on biomolecules has been described (e.g., WO 99/10362, WO 96/19240, and WO 99/43287), but the use of the dendrimeric structures have been directed toward providing signal sites such as for detection while the biomolecule itself is simply attached to a substrate using classical means.
In contrast thereto, the present invention describes an improved process for immobilization of biomolecules using oligonucleotides containing multiple reactive sites, i.e. nucleophiles, electrophiles, and Lewis acids or bases. The advantage of this approach is a higher rate of immobilization, a higher stability of the attachment, and the potential to obtain higher amounts of immobilized oligonucleotide onto the substrate surface. These gains are independent of the approach used for the immobilization. Oligonucleotides with multiple attachment sites can be obtained with both covalent and noncovalent attachment chemistries.
Furthermore the present invention describes the preparation of oligonucleotides containing one or more hydrazides. Hydrazides are nucleophilic reactive groups that can be used for any type of conjugation reaction. They can react, for example, with electrophilic aldehydes forming hydrazones (which can be further stabilized by reduction) and with active esters forming stable covalent linkages, see
The advantages of this invention within the scope of this description are numerous. For example, this invention uses a short reaction time, allows for multiple binding sites per bound entity, provides for stability to a relatively broad pH range, and provides for the capability of attachment under both anhydrous or aqueous conditions thereby providing an improved method for attaching molecules to any solid phase surface for any applicable use. The invention is useful for solid phase synthesis and/or synthesis of small molecule libraries such as biomolecules including, but not limited to, DNA, RNA, PNA, p-RNA (pyranosyl-RNA), and peptides. The invention is also useful for analytical techniques that require an immobilized reagent such as, without limitation, hybridization based assays, diagnostics, gene sequence identification and the like.
In a first embodiment of the invention, biomolecules are provided having a multiplicity of branched or dendrimeric moieties for connecting thereto functional or reactive moieties for binding to a substrate surface.
The use of oligonucleotides with multiple reactive sites or complexing agents within one oligonucleotide offers significant advantages to this immobilization process. First, it increases the speed of the immobilization process. One reason for this effect is that chance for an initial contact between the attachment partners by diffusion is higher when one oligonucleotide bears multiple reactive sites. Additionally, the oligonucleotide can be immobilized via secondary and multiple covalent or noncovalent linkages which are formed after (or simultaneous with) the primary linkage. The formation of these secondary linkages is then an intramolecular process that is kinetically favored to the intermolecular primary linkage formation. This is another reason for the higher immobilization rate.
Second, the overall stability of the attachment increases as multiple linkages are formed between the oligonucleotide and the substrate which is independent of the approach used to bring the biomolecule into contact with the substrate.
The formation of multiple noncovalent complexes results in a higher overall stability of the complex between the oligonucleotide and the substrate allowing the use of low affinity complex builders for a stabile immobilization. Some of the frequently applied immobilization chemistries for oligonucleotides are reversible (e.g. the Schiffs base formation between amines and aldehydes) and require a subsequent stabilization step e.g. by reduction with NaCNBH3. For these reversible reactions the immobilization via multiple linkages is beneficial since it leads in sum to a higher stability of the intermediates formed prior to the stabilization reaction. In some cases the gain in stability is great enough that the stabilization reaction becomes unnecessary.
Third, the use of oligonucleotides with multiple attachment sites allows the production of substrates with higher oligonucleotide loading. Usually the reactive sites on the substrate are in large excess to the oligonucleotides and the improved attachment due to multiple attachment moieties can lead to better use of the available sites on the substrate.
In another embodiment, the multiplicity of reactive binding moieties provided on the biomolecules may allow the biomolecules to bind, either in a covalent or a noncovalent manner, to the substrate surface. With respect to noncovalent binding, the multiplicity of binding moieties may comprise chemical moieties such as biotin, streptavidin, phenyl boronic acid (PBA), and salicyl hydroxamic acid (SHA). With respect to covalent binding, the multiplicity of binding moieties may comprise the use of reactive hydrazide structures. Such structures may be either branched or unbranched thereby allowing for great versatility in the level of possible binding moieties available. Thus, not only are the biomolecules provided with dendritic branching structures, but the reactive binding moieties themselves may also be branched such that each branch has a reactive hydrazide element for use in binding the biomolecule to a substrate surface.
In another embodiment, the multiplicity of binding moieties on the biomolecule provides a means whereby biomolecules attached to a substrate surface comprising an electronically addressable microchip are protected from inadvertent removal from the attachment site on the microchip caused by high voltage and current resulting from electronic biasing of the microchip electrode. Thus, in a preferred embodiment, the multiple attachment scheme of the current invention provides for binding of biomolecules to the substrate capable of withstanding current densities of at least 4 mA/cm2.
In still another embodiment, the invention provides for a method of adding reactive binding moieties to the dendritic structures attached to the biomolecules such that the addition may occur in a single reaction step.
In still another embodiment, the invention provides a composition of matter comprising new chemical modifications of oligonucleotides containing one or multiple hydrazides and thereby the building blocks (e.g. phosphoramidites) for the generation of modified oligonucleotides thereof. These hydrazides comprise reactive groups and can be used for the conjugation of oligonucleotides to fluorophores or other small molecules, to peptides, proteins or antibodies, or to substrate surfaces.
In still another embodiment the attachment scheme can be applied to surface synthesis of biomolecules and analytical applications requiring surface immobilization of compounds.
Referring now to the specific embodiments of the invention, biomolecules are provided having a multiplicity of substrate surface binding moieties.
By “biomolecule” is meant a biologically relevant molecule that is used to contact molecular entities in a test sample. Generally, these include, at least in part, molecules such as nucleic acids, including a single nucleic acid, oligonucleotides and polynucleotides, DNAs, RNAs, CNAs (cyclohexyl nucleic acids), p-MeNAs (methyl or methoxy phosphate nucleic acids), proteins, peptides, enzymes, and antibodies attached to chemical moieties for binding the biomolecule to a substrate surface. Biomolecules also include unnatural or synthetic molecules structurally derived from the naturally occurring molecules such as peptide nucleic acids (PNAs) or p-RNAs (pyranosyl RNAs) attached to chemical moieties for binding the biomolecule to a substrate surface. Having such a binding moiety, biomolecules may also be referred to as “derivatized biomolecules”. Such biomolecules therefore also include oligonucleotides containing oxidized ribose, amine terminations, or any entity of the well known bioconjugate pairs as outlined by Hermanson (Hermanson, G. T. Bioconjugate Techniques copyright 1996, Academic Press, San Diego, Calif.) herein incorporated by reference, and/or alternative nucleic acid structures such as pRNAs (in reference to pRNAs as described in co-pending application Ser. No. 09/374,338 filed Aug. 13, 1999 herein incorporated by reference). Generally, attachment of the chemical moieties to the biomolecules comprises a covalent bond. With respect to attachment of derivatized biomolecules to a substrate surface, such attachment may use either a covalent or a noncovalent bond.
By “polymer” is generally meant macromolecules assembled from the successive linkage of a large number of smaller molecules generally referred to as monomers as recognized by one skilled in the art (for a more detailed description see Odian, G. Principles of Polymerization, Third Edition copyright 1991 John Wiley and Sons Inc., New York, N.Y.). In a preferred embodiment, a homogeneous polymer may be composed of a single type of monomer, while a heterogeneous polymer is be composed of more than one type of monomer. In another preferred embodiment, formation of a polymer can be initiated by thermal decomposition of initiators (e.g. AIBN, benzoyl peroxide), photolytic cleavage of initiators (e.g. UV initiation of Daracur 4265), redox reactions (e.g. cerium (IV) sulfate), ionizing radiation (e.g. α, β, γ or X-rays), plasma initiation (e.g. Argon, Nitrogen, Oxygen), or electrolytic initiation using tetrabutylammonium perchlorate in which the polymerization occurs only over a preselected site using an electric current (Samal, S. K.; Nayak, B. J. Polym. Sci. Polym. Chem. Ed. 1988, 21, 1035.)
By “binding moiety” is generally meant any chemical moiety utilized in the generation of attachment of biomolecules to a substrate surface. A binding moiety may be contained on a biomolecule or contained on a substrate surface. Table 1 Binding Moieties provides a list of binding moieties used.
By “Lewis Base” is generally meant any chemical moiety capable of donating a pair of electrons to an electron deficient center. In a preferred embodiment, a Lewis Base is more specifically referred to as a “nucleophile” in which a reactive center donates a pair of electrons to carbon resulting in a covalent bond between the reactive center and the carbon as recognized by one skilled in the art (For an expanded definition see: Smith, M. B. Organic Synthesis copyright 1994 McGraw Hill Inc., New York, N.Y., or any organic chemistry textbook).
By “Lewis acid” is generally meant any electron deficient chemical moiety capable of receiving a pair of electrons. By “electrophile” is generally meant the specific case in which the Lewis Acid is carbon, as recognized by one skilled in the art (For an expanded definition see: Smith, M. B. Organic Synthesis copyright 1994 McGraw Hill Inc., New York, N.Y., or any organic chemistry textbook). In a preferred embodiment, as an example, salicylic hydroxamic acid is capable of acting as a Lewis base donating a pair of electrons to boron, a Lewis acid, of phenyl boronic acid resulting in a noncovalent linkage. In yet another preferred embodiment, as an example, hydrazide is capable of acting as a nucleophile donating a pair of electrons to the reactive carbon center of an NHS ester, an electrophile, forming a covalent linkage to said carbon center.
By “branched linking moiety” is generally meant any chemical species which is capable of coupling through a specific reactive moiety to a biomolecule and is also capable of further attachment to more than one molecule through alternative reactive centers. In a preferred embodiment, a branched linking moiety is a phosphoramidite of which examples are shown in Table 2, Entries 1-4. In these examples, the phosphorus acts as the reactive moiety while the esters of entries 1, 2, and 3 and the protected alcohols of 4 are alternative reactive centers.
By “branched linking structure” is generally meant a biomolecule resulting from treatment of a biomolecule with a branched linking moiety. The alternative reactive centers of the branched linking moiety are now contained within the branched linking structure. In a preferred embodiment, as an example, a branched linking structure is represented by entry 5 of Table 2 in which the biomolecule shown is the result of treating a biomolecule with a branched linking moiety, specifically the compound displayed in entry 4 of Table 2. In another preferred embodiment the branching linking structure is capable of being combined in a homogeneous series in which a biomolecule is modified with a branching linking moiety, which in turn is further modified by the same branched linking moiety through the alternative reactive centers of the resultant branched linking structure, generating a new branched linking structure. This construction of larger branched linking structures by means of a series of linkages of a branched linking moiety can be further continued as shown in Table 2, Entries 6-8 In yet another embodiment, the branching linking moieties are capable of being combined in a heterogeneous series in which a biomolecule is modified with a branching linking moiety, which in turn is further modified by a different branched linking moiety through the alternative reactive centers of the initial branched linking moiety, generating a new branched linking structure. This construction of larger branched linking structures by means of a series of linkages of branched linking moieties can be further continued as shown in Table 2, Entries 9-12.
By “substrate” is generally meant any material whose surface contains moieties with which the multiple reactive binding moieties of the biomolecules may couple. This substrate can be, among others, a glass slide, a functionalized glass slide, a chemically activated microchip surface, a surface covered with a single or multiple layers of reactive molecules, or a surface covered with a polymer having moieties with which the multiple reactive binding moieties of the biomolecules may react. In a preferred embodiment, a substrate surface is a permeation layer of an electronically addressable microchip. In a preferred embodiment, the functional, chemically active, or reactive moieties of a substrate are selected from (but not limited to) the functional groups listed in Table 1.
By “precursor” is generally meant any reactive moiety which can be transformed to an alternative reactive moiety with treatment of one or more chemical reagents. In a preferred embodiment, as an example, the three ester moieties of 1d, (Entry 3 of Table 2) are precursors to hydrazides. They are transformed to a hydrazide moiety with the treatment of hydrazine.
By “protected” is generally meant blocking the reactivity of a reactive moiety with one or more reagents while a chemical reaction can be carried out at an alternative reactive site of the same compound without obstruction or complication from the initial reactive moiety. Upon completion of the transformation at the alternative reactive site the protecting group of the reactive moiety can be removed, unblocking the reactive center. In a preferred embodiment, a protected moiety is a specific type of precursor. In yet another preferred embodiment, as an example, the hydrazide moiety of 1a of
By “activatable” is generally meant any functional group which is capable of undergoing a transformation to a reactive moiety when treated with one or more chemical reagents. By “activated” is meant a functional group which has undergone such a transformation to a reactive moiety. In a preferred embodiment, an activatable moiety can be a protected moiety or a precursor. In yet another preferred embodiment, the functional group is generally considered benign, unreactive, or incapable of binding to a substrate or biomolecule. Upon treatment with one or more chemical reagents, the functional group is transformed to a moiety capable of binding to a substrate or biomolecule. In a preferred embodiment, as an example, the ester groups of the compounds listed in Table 2 Entries 1-3 are transformed to hydrazides with treatment with hydrazine. In yet another preferred embodiment, as an example, a substrate containing acetal groups is generally considered to be unreactive. Upon treatment with an acidic source, the acetals are transformed to aldehydes which are capable of binding to hydrazide modified biomolecules.
By “microarray” is generally meant a geometric arrangement of a plurality of locations containing defined biomolecules, such individual locations being restricted to linear dimensions of 1 mm or less. Microarrays include an electronically addressable microarray such as an array designated the “APEX chip” as in U.S. Pat. No. 5,632,957 herein incorporated by reference.
1. Preparation of Oligonucleotides with Multiple Attachment Sites
1.1 Oligonucleotide Synthesis with Branching Phosphoramidites:
Branched biomolecule (e.g. oligonucleotides) structures having branched phosphoramidites are commercially available (Chemgenes, Ashland, Mass.; Glenn Research, Sterling, Va.). After one or more consecutive couplings of such branching amidites in the solid-phase oligonucleotide synthesis (
1.2 Direct Introduction of Synthons Having More than One Reactive Group for Attachment:
Alternatively, biomolecules with multiple attachment sites can be obtained by the coupling of special phosphoramidites. These amidites can contain in a protected or precursor from more than one reactive group for the immobilization at the substrate. The reactive group in branched amidites can be again one of the known functionalities such as amino groups, thiols, aldehydes, or hydrazides. Examples for such amidites are shown in
A third approach for the synthesis of biomolecules with multiple reactive groups is the combination of the coupling of branching amidites and amidites with multiple reactive sites (
In a particularly preferred embodiment, biomolecules are provided having a tethered hydrazide for attachment to a substrate surface through a covalent bond. In this embodiment, NHS and Sulfo-NHS and other moieties may be used as a means of activating a substrate or any other type of biomolecule and coupling to biomolecules or even solid surfaces. In the application of the present invention, such attachment provides a novel means whereby biomolecule attachment may be carried out and provide for resistance against damage to tethered biomolecules caused by the extreme reaction conditions associated with electronic addressing of an electronic microchip. Thus, the hydrazide chemistry and multiple attachment scheme of the present invention fulfills requirements for survivability in the environment of an electronic system which requirements include a need for water solubility of the biomolecule, stability to water of the biomolecule and its coupling pair on the immobilizing substrate, and functionality to a pH of approximately pH 4.
The methods by which hydrazide binding moieties were added and utilized in the present invention are provided in the following examples. These examples show site specific covalent attachment of a biomolecule comprising an oligonucleotide in which attachment is accomplished with electronic concentration of a hydrazide-modified oligo onto an N-hydroxysuccinimidyl (NHS) modified polyacrylamide permeation layer above an electronically addressable microarray. The hydrazide moiety of the oligomer displaces the NHS ester forming a bishydrazide linkage. These examples therefore show 1.) Synthesis of the novel hydrazide phosphoramidite (e.g., compound 1) as shown in Example 1 (
Unless otherwise indicated, all reactions were magnetically stirred. Reagents were obtained in analytical grade from Aldrich Chemical Company (Milwaukee Wis.) and solvents from Riedel. Column Chromatography is accomplished using silica gel 60 (Merck, 230-400 mesh). Melting points are uncorrected. IR Spectra are measured on a Perkin Elmer Paragon 1000 FT-IR equipped with a Graseby Specac 10500 ATR unit. 1H-NMR spectra are recorded at 400 MHz; 13C spectra at 100 MHz and 31P at 162 MHz with a Bruker DRX 400 spectrometer. 1H chemical shifts are reported in units of δ using TMS as internal standard, and coupling constants are reported in units of Hz. ESI Mass spectra are recorded on a Finnigan LCQ instrument in negative ionization mode.
To a solution of 6.2 g (20 mmol) of tritylhydrazine hydrochloride (3a) in 200 ml of THF was added 2.22 g (22 mmol, 1.1 eq) triethylamine. The solution was stirred at room temperature (rt) for 15 min, filtered, concentrated to afford compound 3, then treated with 2.29 g (20 mmol, 1 eq) of ε-caprolactone (compound 4). The mixture is heated to 65° C. for 5 h the cooled to rt for 18 h. The precipitate was collected and recrystallized from ethyl acetate to afford 3.55 g (45%) of a white powder (compound 5): 1H-NMR 7.49-7.47 (m, 5H), 7.35-7.10 (m, 10H), 6.55 (d, J=7.52, 1H), 5.55 (d, J=7.25, 1H), 3.54 (t, J=6.45, 2H), 1.87 (t, J=7.25, 2H), 1.62 (bs, 1H), 1.57-1.34 (m, 4H), 1.27-1.11 (m, 2H).
To a solution of 3.0 g (7.7 mmol) N-triphenylmethyl-6-hydroxycapronic hydrazide (compound 5) in 50 ml dry dichloromethane at rt was slowly added 4.0 g (31 mmol, 4 eq) of N-ethyldiisopropyl amine and 2.01 g (8.5 mmol, 1.1 eq) of chloro(diisopropylamino)-β-cyanoethoxyphosphine (compound 6) over 15 min. Upon complete addition, the reaction was stirred for 1 h, concentrated, and chromatographed (ethyl acetate/n-heptane ⅔ with 0.2% triethylamine) to afford 3.19 g (70%) of 1a as a pale yellow foam.
1H-NMR: 7.49-7.46 (m, 5H), 7.34-7.20 (m, 10H), 6.57 (d, J=7.2, 1H), 5.57 (d, J=7.5, 1H), 3.85-3.74 (m, 2H), 3.62-3.48 (m, 4H), 2.62-2.59 (m, 2 H), 1.88-1.84 (m, 2H), 1.53-1.33 (m, 4H), 1.27-1.13 (m, 14H); 31P-NMR (CDCl3): δ=147.97.
To a solution of 1.65 g (10 mmol) of ethyl 6-hydroxyhexanoate (compound 7) in 30 ml dichloromethane at rt are slowly added 5.17 g (40 mmol, 4 eq) of N-ethyldiisopropyl amine and 2.6 g (11 mmol, 1.1 eq) of compound 6 over 15 min. Upon complete addition, the reaction was further stirred for 15 min, concentrated, and chromatographed (ethyl acetate/n-heptane ¼ with 0.2% triethylamine) to afford 2.47 g (69%) of compound 1b as clear oil: 1H-NMR 4.12 (q, J=7.25, 2H), 3.90-3.77 (m, 2H), 3.75-3.55 (m, 4H), 2.64 (t, J=6.44, 2H), 2.30 (t, J=7.25, 2H), 1.69-1.59 (m, 4H), 1.44-1.34 (m, 2H), 1.25 (t, J=7.25, 3H), 1.20-1.12 (m, 12H); 31P-NMR (CDCl3): δ=148.01.
To a solution of 1.29 g (5 mmol) diethyl 5-(hydroxymethyl)isophthalate [252.27] (98%, Aldrich; CAS 181425-91-2) in 20 ml dry dichloromethane at RT are added 2.59 g (40 mmol, 4 eq) N-ethyldiisopropyl amine [129.25] and 1.3 g (11 mmol, 1.1 eq) 2-cyanoethyl N,N-diisopropyl-chloro-phosphoramidite [236.68] (Aldrich; CAS 89992-70-1) over 15 min with stirring. The mixture was concentrated and salts were precipitated with 30 mL ethyl acetate/n-heptane (2:3). The hydrochloride precipitate is filtered; the filtrate is concentrated and directly applied to a chromatography column. Elution with ethyl acetate/n-heptane (1:4) containing few drops triethylamine afforded 1.6 g (70%) 1c as a colorless oil. C22H33N2O6P; 1H-NMR 8.59 (m, 1H, arom.), 8.21 (m, 2H, arom.), 4.87-4.75 (m, 2H, CH2 cyanoethyl), 4.41 (q, J=6.98 Hz, 4H, CH2 ethyl), 3.95-3.80 (m, 2H, 2×CH I—Pr), 3.74-3.61 (m, 2H, CH2 cyanoethyl), 2.66 (t, J (P,H)=6.45 Hz, 2H, O—CH2-arom), 1.41 (t, J=6H, 2×CH3 ethyl), 1.23-1.20 (m, 12H, CH3, I—Pr); 31P-NMR (CDCl3): δ=149.94; 13C-NMR (CDCl3): δ=165.8 (C═O), 140.2 (C—CH2—O—P), 132.1 (2×C arom.), 131.1 (2×C—H arom), 129.7 (C H arom), 117.6 (CN), 64.7 (P—O—CH2-arom), 61.4 (2×CH2 ethyl), 58.6 (O-CH2—CH2—CN), 43.4 (2×C—H I—Pr), 24.7 (4×CH3 I—Pr), 20.5 (O—CH2—CH2—CN), 14.4 (CH3 ethyl); HRMS 453.2156 ([M+H]+C22H34N2O6P requires 453.21545).
To a solution of 300 mg (0.760 mmol) Tris-2,2,2-{[(methoxycarbonyl)ethoxy]methyl}ethanol (CAS 169744-28-9; (Coutts, S.; Jones, D. S.; Livingston, D. A.; Yu, L.: 1995, Chemically-defined non-polymeric valency platform molecules and conjugates thereof, European patent application EP 0642798A2) in 2 ml dry dichloromethane at RT are added two drops of a 0.4 M solution of 1H-Tetrazole in dry acetonitrile (standard activator solution from solid phase DNA synthesis) and 274 mg (0.91 mmol; 1.1 eq) 2-cyanoethyl N,N,N′,N′-tetraisopropylphosphorodiamidite (Aldrich; CAS 102691-36-1) and stirred at RT until TLC shows complete consumption of the starting material (3 h). The solvent is removed in vacuo and the residue is purified by silica gel chromatography. Elution with ethyl acetate/n-heptane (2:3) containing few drops triethylamine afforded 240 mg (53%) of 1d as colorless oil. C26H47N2O11P 1H-NMR (CDCl3): 3.88-3.71 (m, 2H, C—H), 3.68 (s, 9H, CH3 ester), 3.65 (t, J=6.45 6H, 3×CH2—O), 3.62-3.47 (m, 4H, 2×CH2), 3.36 (s, 6H, 3×C—CH2—O), 2.63 (t, J=7.25 Hz, 2H, C—CH2—O—P), 2.54 (t, J=6.45 Hz, 6H, —CH2—COOR), 1.19-1.16 (m, 12H, CH3 iPr); 31P-NMR (CDCl3): δ=148.6; HRMS: 595.2999 ([M+H]+C26H48N2O11P requires 595.29957)
Oligonucleotides are synthesized using solid phase phosphoramidite chemistry on an automated oligonucleotide synthesizer. The phosphoramidite with the protected hydrazide is applied as 0.1 M solution in acetonitrile and coupled at the desired location in the sequence using standard activated reagents and coupling times.
The CPG bound oligo (1 mmol) is placed in a 1.5 ml test tube and treated with 2.0 ml conc. NH4OH. After 2 h at 55° C. the ammonia solution is removed and evaporated to dryness under reduced pressure. The residue is dissolved in 1 ml water and filtered through a 0.45 μm syringe filter. The trityl protected hydrazide oligo is purified by reverse phase HPLC using a Merck LiChrospher RP 18, 10 μM, column (analytical: 4×250 mm, flow=1.0 ml/min; preparative: 10×250, flow=3.0 mL/min) using 0.1 M triethylammonium acetate pH=7.0 (TEAA) as buffer A and 75% acetonitrile in buffer A as buffer B. A gradient of 0% B to 100% B in 100 min is used for analytical and preparative separations. The fractions containing the trityl-on product were pooled and evaporated to dryness.
For the removal of the trityl protecting group the oligo is treated with 80% acetic acid for 30 min at RT. The acid is removed in vacuo, and the residue is dissolved in water then extracted twice with ethyl acetate. The aqueous layer is dried again and re-dissolved. Analytical HPLC usually shows a single product (is some cases as double peak) which can be employed for further reactions without purification. Alternatively HPLC purification can be performed using the solvent system described above.
Oligonucleotides are synthesized using solid phase phosphoramidite chemistry on an automated oligonucleotide synthesizer. The phosphoramidite with the precursor form of the hydrazide is applied as 0.1 M solution in acetonitrile and coupled at the desired location in the sequence using standard activating reagents and coupling times. The use of a phosphoramidite that contains a hydroxyl group labeled with an acid-labile protecting group as well as a hydrazide precursor allows the introduction of the hydrazide at any position of the oligonucleotide because the precursor form of the hydrazide is stabile to the conditions of the oligonucleotide synthesis while the reactive hydrazide is not formed until incubation with hydrazine.
The CPG bound oligo (1 mmol) is treated with a solution of 50 mg diethylamine in 3.5 mL dichloromethane. After incubation overnight (light exclusion) the supernatant is removed and the support bound oligo is washed several times with dichloromethane and dried in vacuo.
For the cleavage of the benzoyl and isobutyryl protecting groups the conversion of the ester at the 5′-end of the oligo to a hydrazide, and the cleavage of the oligo from the support (
A C18 Sep-Pak cartridge (0.5 g Waters, No. 20515) is activated by rinsing with 10 mL acetonitrile and then 10 mL 0.1 M triethylammonium bicarbonate buffer pH 7.0 (TEAB). The hydrazine solution is diluted with the 5-fold volume of TEAB and applied to the cartridge. After binding of the oligo to the Sep-Pak column the residual hydrazine is washed away with 10 mL TEAB. The oligo is then eluted from the column with TEAB/acetonitrile (1:2). Oligo containing fractions are pooled and evaporated to dryness. For the RP-HPLC characterization and purification of the product the same conditions as described in protocol 1 can be applied.
Other examples are provided below wherein oligomers are processed to become linked to the multiple attachment moieties of the invention. The oligos are numbered in sequence of their respective description in this disclosure.
The synthesis and deprotection was performed as described with amidite compound 1a. The trityl ON product elutes at 42.2 min under the conditions described. Oligo 9 elutes at 25.6 min (double peak). LRMS (ESI): M calc.: 4709.15, obs.: 4709.5.
The synthesis and deprotection was performed as described with amidite compound 1a. The trityl ON product elutes at 41.5 min under the conditions described. Oligo 10 elutes at 25.1 min (single peak). HRMS (ESI): M calc.: 6092, obs.: 6092.
The synthesis of the oligonucleotide was performed as described previously. A CPG support loaded with Cy3 dye was used to label the fluorophor at the 3′ end of the oligo. The CPG bound oligo was treated as outlined in Example 1 (E) above and the product was purified by RP-HPLC. The hydrazide oligo elutes at 31.8 min under the HPLC conditions described in Example 1 (D). LRMS (ESI): M calc.: 6599.7, obs.: 6598±2.
For the introduction of multiple hydrazides into oligonucleotides, branching phosphoramidites, phosphoramidites having more than one ester group which are converted into hydrazides, as well as a combination of both approaches were used. This flexible strategy allows the synthesis of oligonucleotides carrying defined numbers between one and up to several (˜40) hydrazides. The experiments herein are described using p-RNA and are applicable to other oligonucleotides such as DNA.
The synthesis of p-RNA oligonucleotides is performed as described in: Miculka, C.; Windhab, N.; Brandstetter, T. Burdinski, G; PCT patent application No. WO 99/15540 (1999) with the following exceptions and modifications: Phosphoramidites of pentopyranosyl nucleosides are dried in vacuo over KOH and dissolved in dry acetonitrile to give a 0.1 M solution. This solution is dried over freshly activated molecular sieve (3 Å) for 3 h and then applied for solid phase oligonucleotide synthesis on a PE Biosystems Expedite 8905 DNA synthesizer. Other phosphoramidites are dissolved at 0.1 M in dry acetonitrile and used without further treatment. For p-RNA oligonucleotides carrying a Cy3 dye at the 2′-end a CPG support custom loaded with monomethoxytrityl protected Cy3 (CAS: 182873-80-9, AP-Biotech, Freiburg, Germany) a 0.1 M solution of anhydrous pyridinium hydrochloride in dry acetonitrile is used as activator. The detritylation time for pentopyranosyl nucleosides is increased to 10 minutes and the coupling time is increased to 25 minutes. All other reagents and solutions and procedures are according to the recommendation of the instrument manufacturer.
For the cleavage of the β-cyanoethyl protecting groups the oligonucleotide is treated with a 1.5% (w/v) solution of diethylamine in dichloromethane overnight at RT (light exclusion). The supernatant is removed and the support bound oligonucleotide is washed several times with dichloromethane and dried in vacuo.
For the cleavage of the benzoyl and isobutyryl protecting groups, the conversion of the esters at the 5′-end of the oligo to hydrazides, and the cleavage of the oligo from the support, the CPG with the bound oligo is treated with 1 ml 24% hydrazine hydrate. After 18 h under constant agitation at 4° C. the reaction is complete. The isolation of the oligo from the hydrazine solution can be achieved by reversed phase extraction (e.g. Sep-Pak or HPLC).
A C18 Sep-Pak cartridge (0.5 g Waters, No. 20515) is activated by rinsing with 10 mL acetonitrile and then 10 mL 0.1 M triethylammonium bicarbonate buffer pH 7.0 (TEAB). The hydrazine solution is diluted with the 5-fold volume of TEAB and applied to the cartridge. After binding of the oligo to the Sep-Pak column the residual hydrazine is washed away with 10 mL TEAB. The oligo is then eluted from the column with TEAB/acetonitrile (1:2). Oligo containing fractions are pooled and evaporated to dryness. The characterization and purification of the products is achieved by reverse phase HPLC using a Merck LiChrospher RP 18, 10 μM, column (analytical: 4×250 mm, flow=1.0 ml/min; preparative: 10×250, flow=3.0 mL/min) using 0.1 M triethylammonium acetate pH=7.0 (TEAA) as buffer A and 75% acetonitrile in buffer A as buffer B. A gradient of 0% B to 100% B in 100 min (HPLC method A) or 30 min (HPLC method B) is used for analytical and preparative separations.
A. Oligo 12: Cy3 Labeled p-RNA Oligo with 1 Hydrazide: p-RNA Oligo 4′-(Hyd1) TAG GCA TT (Cy3)-2′
The synthesis and deprotection was performed as described with amidite compound 1b.
B. Oligo 13: Cy3 Labeled p-RNA Oligo with 3 Hydrazides: p-RNA Oligo 4′-(Hyd3) TAG GCA TT (Cy3)-2′
The synthesis and deprotection was performed as described with amidite compound 1d. The product elutes at 37.9 min (HPLC method A) under the conditions described. LRMS (ESI): M calc.: 3516.6, obs.: 3515.
C. Oligo 14: Cy3 Labeled p-RNA Oligo with 4 Hydrazides: p-RNA Oligo 4′-(Hyd2)2 (SBA) TAG GCA TT (Cy3)-2′
The synthesis and deprotection was performed as described with amidite compound 1c and with symmetric branching phosphoramidite (SBA; Clontech, No. 5252-2). The product elutes at 37.3 min (HPLC method A) under the conditions described. LRMS (MALDI): M calc.: 3784.7, obs.: 3784
D. Oligo 15: Cy3 Labeled p-RNA Oligo with 8 Hydrazides: p-RNA Oligo 4′-(Hyd2)4 (SBA)2 (SBA) TAG GCA TT (Cy3)-2′
The synthesis and deprotection was performed as described with amidite compound 1c and with symmetric branching phosphoramidite (SBA; Clontech, No. 5252-2). The product elutes at 36.9 min (HPLC method A) under the conditions described. LRMS (MALDI): M calc.: 4661.1, obs.: 4464
E. Oligo 16: Cy3 Labeled p-RNA Oligo with Spacer and 8 Hydrazides: p-RNA Oligo 4′-(Hyd)4 (SBA)2 (SBA) (S18) TAG GCA TT (Cy3)-2′
The synthesis and deprotection was performed as described with amidite compound 1c and with symmetric branching phosphoramidite (SBA; Clontech, No. 5252-2) and Spacer 18 (S18, Glen research No. 10-1918-02). The product elutes at 38.7 min (HPLC method A) under the conditions described.
F. Oligo 17: Cy3 Labeled p-RNA Oligo with 16 Hydrazides: p-RNA Oligo 4′-(Hyd2)8 (SBA)4 (SBA)2 (SBA) TAG GCA TT (Cy3)-2′
The synthesis and deprotection was performed as described with amidite compound 1c and with symmetric branching phosphoramidite (SBA; Clontech, No. 5252-2). The product elutes at 38.7 min (HPLC method A) under the conditions described.
G. Oligo 18: p-RNA Oligo with 4 Hydrazides (without Cy3 Dye): p-RNA Oligo 4′-(Hyd2)2 (SBA) TAG GCA TT-2′
The synthesis and deprotection was performed as described with amidite compound 1c. The product elutes at 12.75 min (HPLC method B) under the conditions described. LRMS (ESI): M calc.: 3275.1, obs.: 3275.4.
50 nmol hydrazide oligonucleotide are dissolved in 200 μL 10 mM ammonium acetate buffer pH 4.0 and 15 equivalents of 4-Formylphenlyboronic acid (Aldrich No. C43, 196-6; CAS: 87199-17-5) per hydrazide are added. For an oligonucleotide containing 4 hydrazides for example 30 μL of a 0.1 M solution of 4-Formylphenlyboronic acid in DMSO (3 μmol) are used. The mixture is incubated at RT for 1 h, 20 equivalents NaCNBH3 per 4-Formylphenlyboronic acid are added and incubation is continued for one other hour at RT. For example for the oligonucleotide with 4 hydrazides 150 μL (150 μmol) of a 1 M solution of NaCNBH3 in 10 mM ammonium acetate buffer pH 4.0 (6.3 mg dissolved in 1 mL) are necessary.
The removal of excess 4-Formylphenlyboronic acid and Sodium Cyanoborohydride are removed by means of HPLC, gel filtration (Pharmacia PD 10 columns), or solid phase extraction (Merck LiChrolute columns). For boronate modified oligonucleotides it is crucial to use an endcapped HPLC column. Typical conditions are 5 μm Phenomenex Luna Phenyl Hexyl columns (analytical: 4.6×250 mm, flow=1.0 ml/min; preparative: 10×250, flow=3.0 mL/min) using 0.1 M triethylammonium acetate pH=7.0 (TEAA) as buffer A and 75% acetonitrile in buffer A as buffer B. A gradient of 0% B to 100% B in 100 min (HPLC method A) or 30 min (HPLC method B) is used for analytical and preparative separations. Product containing fractions are pooled and evaporated to dryness.
A. Oligo 19: p-RNA Oligo with 1 Boronate: p-RNA Oligo 4′-(PBA) TAG GCA TT (Cy3)-2′
The synthesis and deprotection was performed as described in the general protocol using oligonucleotide 12 as starting material.
B. Oligo 20: p-RNA Oligo with 3 Boronates: p-RNA Oligo 4′-(PBA)3 TAG GCA TT (Cy3)-2′
The synthesis and deprotection was performed as described in the general protocol using oligonucleotide 13 as starting material.
C. Oligo 21: p-RNA Oligo with 4 Boronates: p-RNA Oligo 4′-(PBA)4 (SBA) TAG GCA TT (Cy3)-2′
The synthesis and deprotection was performed as described in the general protocol using oligonucleotide 14 as starting material.
D. Oligo 22: p-RNA Oligo with 8 Boronates: p-RNA Oligo 4′-(PBA)8 (SBA)2 (SBA) TAG GCA TT (Cy3)-2′
The synthesis and deprotection was performed as described in the general protocol using oligonucleotide 15 as starting material. The product elutes at 46.3 min (HPLC method A) under the conditions described.
E. Oligo 23: p-RNA Oligo with Spacer18 and 8 Boronates: p-RNA Oligo 4′-(PBA)8 (SBA)2 (SBA) TAG GCA TT (Cy3)-2′
The synthesis and deprotection was performed as described in the general protocol using oligonucleotide 16 as starting material.
F. Oligo 24: p-RNA Oligo with 16 Boronates: p-RNA Oligo (PBA)16 (SBA)4 (SBA)2 (SBA) TAG GCA TT (Cy3)-2′
The synthesis and deprotection was performed as described in the general protocol using oligonucleotide 17 as starting material. The product elutes at 49.0 min (HPLC method A) under the conditions described.
G. Oligo 25: p-RNA Oligo with 1 Boronate: p-RNA Oligo 4′(PBA)-TAG GCA TT (Cy3)-2′
The synthesis and deprotection was performed as described in the general protocol using oligonucleotide 18 as starting material.
Upon completion of the synthesis of hydrazide oligos, the first set of experiments examined the solution reaction kinetics of a hydrazide labeled oligo with an NHS or Sulfo-NHS ester. To a solution of 5 uL of 132 uM hydrazide ATA5 in 30 uL of 50 mM histidine was added 5 uL of 10 mM NHS acrylate. The solution was stirred at RT for a short period of time then injected into an HPLC system. The HPLC trace of the compounds in the solution indicated the quantities of hydrazide ATA5 and N′acrylo-ATA5 dihydrazide present in the reaction mixture for a given reaction time. The retention times of the starting ATA5 hydrazide and the modified ATA5 hydrazide were distinct and separable.
Comparison of this rate to other attachment systems utilized is shown in
Microarray containing chips are plasma cleaned 5 minutes under Argon. The 25 site 1 cm by 1 cm chips are then silanized using vapor phase deposition. To the center of the microarray is added 0.10 uL of a 20% (by mass) solution of 9:1 (molar ratio) acrylamide/bisacrylamide in 1:1 DMSO/H2O with 0.3% Daracur 4265 as a UV initiator. The chip is placed into a microreaction molding system to which the microarray site is pressed to a UV window containing a square 4 uM cavity, 3.mm on a side. The solution is irradiated for 20 sec with UV light, removed from the molding system, rinsed with water and air dried. The well forms a square hydrogel layer over the microarray. Excess polymerization, beyond the parameters of the mold, is removed.
To the existing permeation layer is added 0.80 uL of a solution containing 20% (by mass) monomer concentration of NHS or Sulfo-NHS/Am/Bis 10/83/7 (molar ratio) and allowed to saturate the existing polymer for 1 minute. The chip is loaded onto the microreaction molding system and polymerized as above with a circular mold with a diameter of 4.6 mm and a well depth of 5 uM. This second mold completely encompasses and extends beyond the existing square layer. Attachment of the second layer is accomplished through intercalation of polymer chains and bind silane. The chips are washed with water and dried with compressed air and subsequently tested in the following experiments.
To chips modified with the two fold permeation layer as described above containing 0, 1, 2 and 4% Sulfo-NHS was electronically loaded 500 hydrazide-T12-BTR as a specific labeled capture while 50 mM nM biotin-T12-BTR was used as a nonspecific labeled capture. All solutions were buffered in 50 mM histidine. Captures were addressed at a current of 500 nA/pad for 120 seconds, 4 pads at a time. Each chip was washed with 1% SDS, 0.2×STE and soaked in 1% SDS for 20 minutes. The chips were imaged for 1 second and the average MFI values were recorded.
As can be seen by in
To chips modified with the two fold permeation layer as described above containing 10% NHS or Sulfo-NHS was electronically loaded 500 and 5 nM hydrazide-T12-BTR as a specific labeled capture. 500 mM nM biotin-T12-BTR was used as a nonspecific labeled capture. All solutions were buffered in 50 mM histidine. Captures were addressed at currents of 400, 500, 600, 700 and 800 nA/pad for 120 seconds, 3 pads at a time. Nonspecific captures were loaded at 800 nA/pad. Each chip was washed with 1% SDS, 0.2×STE and soaked in 1% SDS for 20 minutes. The chips were imaged for 1 second and the average MFI values were recorded.
As can be seen by in
To chips modified with the two fold permeation layer as described above containing 10% NHS were loaded Cy3 labeled ATA5 oligos containing 1, 2, 4, or 8 hydrazide moieties. The four oligomers were electronically addressed at 500 nM with a current of either 700 or 800 nA/pad for 120 s, buffered in 50 mM histidine. Upon completion, the chips were washed and the binding levels were measured.
The recorded MFI/s values are displayed in
To chips modified with the two fold permeation layer as described above containing 15% NHS was loaded an octa-hydrazide ATA5 oligomer with a Cy3 label as a specific capture. The specific capture was loaded at 500 nM with a current of either 600 or 700 nA/pad for 120 s, buffered in 50 mM histidine. Electronic Hybridization was carried out with 5 nM RCA5-T12-Cy5 as a specific target while a solution of 5 nM RCA4-Cy5 was used as a nonspecific target. The targets were loaded at 400 nA/pad for 60 seconds, the chips were washed according to the standard protocol and imaged.
The data presented in
The PBA-containing branched oligonucleotides were purified and analyzed by HPLC. The HPLC of PBA-containing oligonucleotide showed a broader peak than that of a regular oligonucleotide.
20 nM non-branched and branched PBA-containing ATA5 capture probes were loaded on hydrogel substrates electronically. The capture probes were loaded in 50 mM histidine, 10 pads at a time for 120 seconds. 20 nM RCA5-BTR was loaded passively for 5 minutes. The substrates were washed and imaged. Analysis showed that both branched and unbranched capture probes were immobilized to the permeation layer, as desired.
Oligos 20, 21 and 22 (p-RNAs containing 3, 4, and 8 PBA binding sites) were electronically addressed to SHA modified hydrogel chips. Upon completion, initial images were recorded after a standard washing procedure previously described. The chip arrays were then subject to regular irrigation with repeated rinsing with 10 uL of 50 mM histidine. Images were recorded after 5 washings. The results shown in
Previously, oligos modified with a single amine or hydrazide have been electronically loaded onto aldehyde modified hydrogels. The interaction of an aldehyde with an amine or hydrazide results in the formation of an imine (carbon with a double bond to nitrogen) or a hydrazone respectively. These moieties are reversible under aqueous conditions and require further reduction with NaBH3CN to form a stable irreversible covalent attachment. Indeed, electronic concentration of an oligomer containing a single hydrazide resulted in attachment of the oligomer to the surface via hydrazone formation. Elimination of the reduction step resulted in a readily hydrolyzed and unstable linkage in which the bound oligo readily diffused away. The use of dendrimeric hydrazides provides a means of covalent attachment through a somewhat unstable linkage which does not require further reduction; provided there are a significant number of hydrazones formed per oligo. The reversible hydrazone formation can occur with some linkage sites while others remain intact (
Standard 25 site chips were spin coated with glyoxyl agarose (FMC, Princeton, N.J.)). 500 nM Hydrazide Cy3 labeled oligos containing 1, 2, 4, and 8 hydrazides were electronically loaded at 500 nA/pad for 2 minutes each, buffered in 50 mM histidine. The chips were washed according to established procedure and imaged. The recorded MFI/s values are displayed in
Standard 25 array site microchips were modified with a single layer hydrogel composed of acrylamide, bisacrylamide and vinyl acetal in a 15:2:3 ratio. Selected sites were predisposed to a current of 300 nA/pad for 2 minutes in a 50 mM NaCl solution to hydrolyze the acetal functionality exposing the aldehydes. Dendrimeric hydrazide oligomers containing 8 hydrazides per oligo were electronically loaded at 500 nA/pad for 2 minutes buffered in 50 mM histidine to pads which had been activated and to those that had not. A nonspecific oligo was also electronically loaded onto both acetal and aldehyde modified sites. After a standard wash cycle, the chips were imaged. The recorded MFI/s data is displayed in
As can be seen in
10 μmol Hydrazide Oligonucleotide 9 are dissolved in 60 μL 10 mM ammonium acetate buffer (pH 4.0). 1 drop benzyloxyacetaldehyde (CAS: 6065-87-3; C9H10O2 [150.1760] Aldrich No. 38, 218-3) is added and the mixture is allowed to stand at RT for 1 h. The solvent and excess of aldehyde is removed in vacuo and the product is analyzed by HPLC (Column: Merck LiChrospher RP 18, 10 μM, 4×250 mm; Buffer A=0.1 M triethylammonium acetate pH=7.0, Buffer B=75% acetonitrile in buffer A; Flow=1.0 mL/min; Gradient: 0% B to 100% B in 100 min). The retention time of the product is 30.7 min, oligo 9 elutes at 25.5 min.
4.4 nmol Oligo 10 are dissolved in 60 μL 10 mM ammonium acetate buffer (pH 4.0). 44 nmol (10 eq.) antipain hydrochloride (CAS: 37682-72-7; C27H44N10O6.2 HCl; [677.6304]; Calbio No. F 178220) in 15 μL buffer are added and agitated 3 h at RT. The intermediate product is reduced with NaBH3CN (100 eq.) for 1 h at RT. The product is isolated by HPLC (Column: Merck LiChrospher RP 18, 10 μM, 4×250 mm; Buffer A=0.1 M triethylammonium acetate pH=7.0, Buffer B=75% acetonitrile in buffer A; Flow=1.0 mL/min; Gradient: 10% B to 85% B in 60 min). The retention time of the product (oligonucleotide peptide conjugate) is 16.5 min, oligo 10 elutes at 13.9 min. MS (ESI): calc: 6680.6; obs.: 6679.6)
For the binding of hydrazide modified oligonucleotides to commercially available slides a series of p-RNA oligonucleotides containing 1 to 16 hydrazides were used. Along with oligonucleotides 12, 13, and 14, oligomers with 3 and 6 hydrazides, prepared from 1d, were used. Additionally, an amine terminated oligomer (prepared with 5′ Amino Modifier C6; Glenn Research) and an oligonucleotide without modification are used as nonspecific controls. All oligomers are labeled with Cy3 at the 2′ end and retain the same nucleotide sequence.
Oligonucleotides are dissolved in 3D Link™ print buffer (Surmodics, Inc, Eden Prairie, Minn.) at pH=8.5 with concentrations ranging between 10 μM and 100 nM. From each solution, 0.5 μL was applied directly to the slide surface and incubated at room temp. in a sealed chamber above a saturated NaCl solution overnight in the dark. The slides are then treated for 15 min at 50° C. with 3D Link™ blocking buffer to block unreacted surface sites. The slides were washed twice with water followed by a 30 min wash with 0.2% SDS at 50° C. and finally two water washings, then allowed to air dry. The fluorescence detection was preformed on a Pharmacis scanner with 20 second integration times. Images as well as intensity profiles are displayed in
The nonspecific oligonucleotide afforded a signal between 10×103 and 25×103 relative units at 10 μM. The signal compares in intensity with that observed for an oligonucleotide containing a single amino group. In contrast, the hydrazide modified oligonucleotide affords a much higher loading of 35-40×103 fluorescence units. Further, the hydrazide modified oligonucleotide has a higher fluorescence signal at lower concentrations, with a lower limit of detection of 1.25 μM, as compared to the amine modified oligomer which has a lower detection limit of 5 μM.
Oligonucleotides are dissolved in either Surmodics 3D Link™ print buffer at pH=8.5 with concentrations ranging from 10 μM to 100 nM or in 10 mM ammonium acetate buffer at pH=4.0. From each solution, 0.5 μM are applied to the surface of SuperAldehyde slides (Telechem International, Inc Sunnyvale, Calif.) and allowed to incubate overnight at rt. The slides are then treated twice with 0.2% SDS and washed 4 times with water (2 min each). The surface was then treated with a solution of 0.3% NaBH3CN in PBS buffer, pH=7, with 133 mL ethanol to eliminate bubbling. This was followed by three 1 min washings with 0.2% SDS and water. Fluorescence detection was preformed on a Pharmacis scanner with 20 s integration times. Images as well as intensity profiles are displayed in
As can be seen if
The foregoing is intended to be illustrative of the embodiments of the present invention, and are not intended to limit the invention in any way. Although the invention has been described with respect to specific modifications, the details thereof are not to be construed as limitations, for it will be apparent that various equivalents, changes and modifications may be resorted to without departing from the spirit and scope thereof and it is understood that such equivalent embodiments are to be included herein. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.
